The present invention relates to detection of defective commodities which travel along a predetermined path and are randomly distributed among satisfactory commodities. More particularly, the invention relates to a method and apparatus for detecting and segregating defective commodities, such as packs of cigarettes or other rod-shaped smokers' products, which are transported along a predetermined path and must be removed from such path while the satisfactory commodites advance through and beyond the monitoring and ejecting stations. Still more particularly, the invention relates to improvements in a method and apparatus for detection and segregation of defective packs which contain cigarettes, cigars or other rod-shaped or particulate smokers' products and whose defectiveness is attributed or attributable (either exclusively and/or among other causes) to the absence of acceptable inner, outer and/or intermediate envelopes for the confined material or articles.
U.S. Pat. No. 4,053,056 granted Oct. 11, 1977 to Day (and corresponding to German Offenlegungsschrift No. 2,731,477 or United Kingdom Pat. No. 1,545,728) discloses an apparatus wherein a series of cigarette packs is transported along an elongated path which is defined by the normally parallel inner reaches of two endless belts trained around pulleys which rotate about vertical axes. The inner reaches of the two belts are driven at the same speed and advance in the same direction to grip the respective sides of successive packs which are introduced into the aforementioned path. The packs are spaced apart from each other. The condition of successive packs of the series of packs in the path between the inner reaches of the two belts is monitored and, when the detector system ascertains the presence of a defective pack, it generates a signal which is transmitted to an ejecting device which increases the distance between the inner reaches of the belts so that the defective packs descend by gravity.
A drawback of the just described patented apparatus is that the mechanism which increases the distance between the inner reaches of the two belts comprises a relatively large number of complex, sensitive and expensive parts. Moreover, the space requirements of the patented apparatus are quite substantial because only one pack can be disposed in the aforementioned path at a time; otherwise, the widening of the path for the purpose of ejection therefrom of a defective pack would or could result in ejection of one or more satisfactory packs which immediately precede and/or follow the defective pack. An additional drawback of the patented apparatus is that the belts are subjected to frequent and quite pronounced stresses so that their useful life is rather limited. Since the path along which the packs advance during testing and/or ejection is relatively long, the output of the apparatus is relatively low except if the belts are driven at an extremely high speed which is likely to interfere with reliable operation of the monitoring means. On the other hand, rapid transport of packs is desirable if the combined monitoring and segregating apparatus is installed immediately downstream of a modern high-speed packing machine which turns out several hundred cigarette packs per minute.